1. Field of the Invention
The present invention relates to wireless communications systems and, more particularly, to systems and methods for detecting radar signals in wireless communications systems.
2. Description of Related Art
Wireless communications products that support the IEEE 802.11a standard may communicate using unlicensed frequency bands at around 5 GHz. There are existing radar systems that also operate in some of these frequency bands. Such radar systems are typically associated with public safety and security functions such as air traffic control, military, etc. Wireless communications systems are therefore often required by relevant authorities to give way to radar systems. In general, if there is a radar system actively operating on a particular channel in one of these bands that is shared by 802.11a devices, all 802.11a devices must detect the presence of radar and avoid using the particular channel.
Wireless communications systems may include radar detecting components that perform processes for managing the sharing of the spectrum between 802.11a and radar systems. Operation of such processes may be governed by a Dynamic Frequency Selection (DFS) specification. Various regulatory bodies around the world tend to have their own version of a DFS specification. For example, the United States (care of the Federal Communications Commission, or the FCC), Europe (care of the European Telecommunications Standards Institute, or the ETSI), and Japan each enforce versions of the DFS specifications.
Currently, the DFS enforced in the US contains the most stringent requirements in terms of the number of radar waveform types to be detected. The FCC's DFS Specification specifies that 802.11a devices detect 3 types of radar waveforms: (1) a time-invariant waveform with fixed parameters, (2) a time-invariant waveform with a range of parameters, and (3) a time-varying waveform. In Europe and Japan, the respective DFS specifies that a time-invariant waveform with fixed parameters. Wireless system communications system providers may be designed to conform with the DFS from more than one jurisdiction. Typical solutions for detecting radar employ software-implemented algorithms.
It would be desirable to implement a hardware-based system capable of detecting all three types of waveforms specified by the different DFS's.